Ok this will be editing the deathrally.ini file,
It will allow you get all weapons, change weapon and vehicle values.
Lets start by getting the file, it is in /data/data/com.remedy.DeathRallyFREE/app_dr_data/dr/Risoursa/DeathRally.ini
From here you can edit Individual Stats for almost everything.
MAKE SURE YOU BACK UP YOUR FILES
Also make sure to know that weapon and vehicle changes will also affect the computers weapons/cars.
The way I did it is lower the base stats to 1, making the computer slower. and putting steps (upgrades to 7(5 for armor)) let me upgrade way past the enemy.
This modification will allow you to pick up a part "almost every race"
The top will give you rapid fire.
But look closely to the weapon stats, if you moddify them to high the computers weapons will kill everything in a few seconds.
I recommend just changing the "levels" to 20 and the "ammoCountMax" to a 1000.
If you can't edit just download this edited .ini FILE and replace the original .... Have a backup of original ...
Good luck, I will help if you have any problems.